Colorectal Cancer ____________________________________________________________________________
EFFICACY OF COLORECTAL CANCER SCREENING TESTS
Screening Approach
Magnitude of Effect
Effect on colorectal cancer mortality reduction Fecal occult blood test (FOBT)
15% to 33%
Fecal occult blood test (fecal immunochemical-based, FIT)
Fair
Sigmoidoscopy
About 22% to 31%; 13% to 50% for distal colon
Digital rectal examination
No effect
About 60% to 70% for left colon, uncertain for right colon
Colonoscopy
Effect on incidence Sigmoidoscopy
20% to 25%
FOBT
Likely small to none
Colonoscopy
About 60% to 70% for left colon; uncertain for right colon
Immunochemical FOBT
Fair
Source: [1]
Table 4
Adequacy of bowel preparation should be assessed after com- pleting appropriate efforts to clear residual bowel debris. The rate of adequate preparation should be routinely recorded, and adequate patient preparation should be achieved in at least 85% of all examinations per physician [138]. Split-dose bowel-cleansing regimens are strongly recommended for screening colonoscopy. A same-day regimen is an acceptable alternative to split dosing, especially for patients undergoing afternoon examination. The second dose of split preparation should ideally begin four to six hours before the time of colo- noscopy, with completion of the last dose at least two hours before the procedure time. With split-dose bowel-cleansing regimens, diet recommendations include low-residue or full liquids until evening on the day before colonoscopy. Healthcare professionals should give oral and written patient instructions for all components of colonoscopy preparation and emphasize the importance of compliance. The physician performing the colonoscopy should ensure that appropriate support and process measures are in place for patients to achieve adequate colonoscopy preparation quality. Selection of a bowel-cleansing regimen should consider patient’s medical history, medications, and, when available, previously reported bowel preparation adequacy. A split-dose regimen of a 4-L polyethylene glycol electrolyte lavage solu- tion (PEG-ELS)-based cleansing agent provides high-quality bowel cleansing. In healthy, non-constipated individuals, a 4-L PEG-ELS formulation produces a bowel-cleansing quality comparable to lower-volume PEG formulations. Over-the-counter bowel cleansing agents have variable efficacy depending on the agent, dose, timing of administration, and whether used alone or in combination. Regardless of the agent, efficacy and tolerability are enhanced with a split-dose regimen.
Although over-the-counter purgatives are generally safe, caution is required in certain populations, such as strictly avoiding magnesium-based preparations in patients with chronic kidney disease. Routine use of adjunctive agents for bowel cleansing before colonoscopy is not recommended. Split-dose bowel cleansing is associated with greater willingness to repeat the regimen compared with day-before regimens. In addition, low-volume bowel cleansing agents are associated with greater compliance in repeat colonoscopies. There is insufficient evidence to recommend specific bowel preparation regimens for children, adolescents, and elderly persons, but sodium phosphate preparations should be avoided in the elderly, in children younger than 12 years of age, and in those with risk factors for complications from this medication, including known or suspected inflammatory bowel disease. Additional bowel purgatives should be considered in patients with risk factors for inadequate preparation. Low-volume preparations or extended time delivery for high-volume preparations are recommended for patients after bariatric surgery. Tap water enemas should be used to prepare the colon for sigmoidoscopy in pregnant women. There is insufficient evidence to recommend specific regimens for persons with a history of spinal cord injury; additional bowel purgatives should be considered. There is also insufficient evidence to recommend a single salvage strategy for patients whose poor preparation precludes effective colonoscopy completion. In these cases, large-volume enemas may be attempted in patients who present for colo- noscopy and report brown effluent despite compliance with the colon-cleansing regimen. Through-the-scope enema with completion of colonoscopy the same day may also be consid- ered, especially for patients receiving propofol sedation. Wak-
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